156 Biological Stains 



In actual practice, however, the names applied to this group 

 of dyes are very loosely employed, and one is often furnished 

 under such a label as dahlia or Hofmann's violet a mixture of basic 

 fuchsin and methyl violet, having a shade about the same as one 

 of the compounds just mentioned. Two samples of * 'dahlia" 

 have been called to the attention of the Commission which actu- 

 ally differed very greatly, one being nearly as red as fuchsin, the 

 other nearly as blue as methyl violet. There was every reason to 

 believe that one was a fuchsin with a small addition of methyl 

 violet, the other a methyl violet with a little fuchsin added. The 

 latter dyes are much more cheaply prepared than the true Hof- 

 mann violets, and the substitution is natural considering that the 

 shade obtained can be the same. 



Hofmann's violet has been called for by Ehrlich and by Unna 

 for staining mast cells; by Juergens for staining amyloid, which it 

 colors red, while the cytoplasm is colored blue. (See Krause, 

 1926-7, p. 1123). Now it is possible that for one of these pro- 

 cedures or for some other similar one, a true Hofmann's violet is 

 necessary; on the other hand the shade obtained may be the im- 

 portant matter, in which case as satisfactory results should be ob- 

 tainable with a mixture of fuchsin and methyl violet. This is a 

 matter that should be further investigated; for if the cheaper 

 fuchsins and methyl violets can be substituted for the Hofmann 

 violets, the substitution can be made by the biologist himself. It 

 is interesting to remark that one supply house not long ago sent out 

 a bottle of crystal violet, unintentionally mislabeled dahlia, to a 

 biologist ordering the latter dye. This biologist shortly wrote to 

 the company that he would like more of it, as it was the best lot of 

 dahlia he had ever used; in looking the matter up to duplicate the 

 former order, the company discovered its mistake. 



It is extremely difficult to determine just what dye in this group 

 is referred to by any given name. Thus a rosanilin violet has 

 been mentioned as having been employed in a stain for Negri 

 bodies; and it is uncertain whether it is a dye of the above group or 

 of the group following. Any biologist employing one of the violet 

 rosanilins should be especially careful in publishing his work to 

 give all the information furnished on the label as to manufacturer 

 and the nature of the dye; and should preferably verify all such 

 work, before publication, by using a dye of known composition. 



n25 methyl violet c. I. NO. 68o 



Synonyms : Dahlia B. Paris violet. Pyoktaninum coeruleum. 



Gentian piolet. 



Various shades denoted: Methyl violet 2R, R, B, 2B, 3B, 

 BBN, BO, V3. 



